What is CVE-2021-40834?

CVE-2021-40834 is a medium-severity vulnerability in F-Secure Mobile Security, classified under Improper Restriction of Rendered UI Layers or Frames (Clickjacking). CVSS score: 4.3/10. Published 2021-12-10.

How severe is CVE-2021-40834?

Medium severity. CVSS v3 base score is 4.3 out of 10.

Vulnerability in F-Secure Mobile Security

CVE-2021-40834

A user interface overlay vulnerability was discovered in F-secure SAFE Browser for Android. When user click on a specially crafted seemingly legitimate URL SAFE browser goes into full screen and hides the user interface. A remote attacker can leverage this to perform spoofing attack.

Published 2021-12-10 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 4.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:U/C:L/I:L/A:L.

EPSS exploit prediction

EPSS: 0.008 (54.9th percentile), scored 2026-10-31.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 55th percentile — 54.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.007 · newest: 0.008 · change: +0.000

Affected products

F-Secure Mobile Security — versions 18.5x
F-Secure Safe

Weakness classification (CWE)

CWE-1021 — Improper Restriction of Rendered UI Layers or Frames (Clickjacking)

References

www.f-secure.com/en/business/programs/vulnerability-reward-program/hall-of-fame (Vendor Advisory)
www.f-secure.com/en/business/support-and-downloads/security-advisories/cve-2021… (Vendor Advisory)

Frequently asked questions

What is CVE-2021-40834?: CVE-2021-40834 is a medium-severity vulnerability in F-Secure Mobile Security, classified under Improper Restriction of Rendered UI Layers or Frames (Clickjacking). CVSS score: 4.3/10. Published 2021-12-10.
How severe is CVE-2021-40834?: Medium severity. CVSS v3 base score is 4.3 out of 10.